KR102405126B1 - Asymmetric light intensity distribution from the luminary - Google Patents

Abstract

In one embodiment, an overhead street lamp (luminary) is formed with an asymmetric light intensity distribution in which the peak intensity is greatest along the direction of the street, lower directly across the street, and much lower on the house side of the street. . Around the edge of a circular transparent light guide are white light LEDs that inject light into the light guide. To help control the asymmetry of the light intensity distribution, serrated grooves are formed in the light guide surface opposite the light emitting surface and parallel to the distance. Gaussian diffusers are used to partially diffuse the light. By proper selection of the grooves, the Gaussian diffuser, and the relative amounts of light emitted by the LED segments around the light guide, the desired asymmetric light intensity distribution is achieved with direct observation of the light exit surface appearing as uniform light.

Description

Asymmetric light intensity distribution from the luminary

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on U.S. Provisional Patent Application No. 62/298,355, filed on February 22, 2016, U.S. Provisional Patent Application No. 62/328,402, filed on April 27, 2016, and European Patent Application No. 62/328,402, filed on June 7, 2016 Application No. 16173295.3 claims priority. U.S. Provisional Patent Application No. 62/298,355, U.S. Provisional Patent Application No. 62/328,402, and European Patent Application No. 16173295.3 are incorporated herein by reference.

field of invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to general lighting devices using light emitting diode (LED) lamps, in particular luminaries that produce an asymmetric light intensity distribution suitable for illuminating a street, narrow street, wall, or other area. is about

Conventional street lights are being replaced by more efficient and more reliable LED luminaries. The desired light intensity distribution provides the highest peak light intensity along the distance and very little light intensity in the direction opposite the distance. The side of the luminary facing away from the street is referred to herein as the “house side” and the side of the luminary facing the street is referred to herein as the “street side”. The light intensity in the direction of the house side should only be sufficient to illuminate the sidewalk or curb along the street.

Modern street lights using LEDs use asymmetric lenses over high power LEDs to control the light intensity distribution. Alternatively, conventional auxiliary optics are used to direct light down and sideways while blocking the light from being emitted toward the house side. These street lights give the viewer a strong glare when looking directly at the luminary. For example, one type of street light uses two parallel rows of eight high power white light LEDs with a separate lens over each LED. When viewed directly, 16 very bright point light sources are visible. This is called pixelated lighting and is aesthetically undesirable.

What is needed is an efficient luminaire that uses LEDs with a controllable asymmetric light intensity distribution, such as optimized for overhead street lights, where the luminary has a non-pixelated pattern when viewed directly.

In one embodiment, an overhead street lamp (luminary) is formed with an asymmetric light intensity distribution in which the peak intensity is highest along the direction of the street, lower directly across the street, and much lower on the house side of the street. . The intensity distribution may be a mirror image perpendicular to the distance.

The luminary includes a circular, transparent light guide, such as about 15 inches (38 cm) in diameter and about 0.5 cm thick. A circular metal frame supports the light guide. Around the edge of the light guide are white light LEDs on a flexible strip that inject light into the polished edge of the light guide to maintain directivity.

The LEDs on the strip are divided into segments, such as 12 segments (according to the size of the luminary). The segments may be designed or controlled to emit different amounts of light to help create a desired asymmetric light intensity distribution. The amount of light emitted by each segment can be controlled by changing the number of LEDs in each segment or by changing the current to each segment. In another embodiment, the light emission from each segment is the same. Each segment may include LEDs connected in series, and the segments may be connected in parallel.

In another embodiment, the LEDs are arranged in a variable pitch or density to achieve a desired azimuthal light intensity distribution (ie, in a horizontal angular plane), and potentially one or more rows of LEDs depending on the required concentration. .

Light injected into the light guide reflects internally until it is extracted, so that the light is mixed to some extent within the light guide while still having some directivity.

To also control the asymmetry of the light intensity distribution, parallel serrated grooves are formed in the light guide surface opposite the light emitting surface. The grooves are parallel to the distance.

In one embodiment, all grooves are the same and their angles and spacing can be designed to fine tune light distribution and luminance uniformity over the emitting surface. Since the angled surfaces of the grooves are generally directed to the house side LEDs and the vertical surfaces of the grooves are generally directed to the street side LEDs, the rays from both the house side LEDs and the street side LEDs are generally directed to the groove surface. After being reflected from the fields, it is directed towards the distance. The spacing between the grooves can be varied along the light guide to more evenly distribute the light across the light exit face of the light guide.

In another embodiment, the angles and depths of the sawtooth grooves increase gradually towards the distance side to reduce the amount of light reflected back towards the house side and further improve the luminance uniformity above the emitting surface. improve

Translucent dots, such as epoxy-based dots, can be printed on the light-emitting side of the light guide, which can increase light extraction efficiency and help widen the distance-side beam. The dots are about 1 mm in diameter and can have Gaussian light emission (as opposed to Lambertian). Gaussian dots spread the incident ray somewhat along the direction of the incident ray, such as providing a 12 degree half width, half maximum spread. The dots are uniformly arranged on the surface of the light guide and may occupy about half the area of the light emitting surface. Alternatively, the dots may have a variable size distribution or a variable density distribution to improve luminance uniformity over the entire light emitting surface.

A continuous diffusing layer or surface texture of Gaussian (such as a somewhat "frosted glass" finish) may also be used in place of the dots.

These diffusing elements may also be disposed on the rear surface of the light guides and alternate with grooves. Light from the diffusing elements will be further mixed within the light guide to increase uniformity.

A reflector is disposed above the light guide to reflect back any upward light exiting the light guide.

An additional transparent optical plate inserted below the exit face of the light guide can be used to protect the light guide and provide some additional light distribution control, for example to filter out high angle rays to reduce glare. Tissue may further be added to the light guide surface to reduce or suppress light directed towards the house side.

By proper selection of the grooves, the relative amounts of street side lighting and house side lighting can be controlled. By controlling the amount of light emitted by each LED segment, the asymmetric light intensity distribution can be further controlled. By using Gaussian dots (or other suitable diffusers), the light exiting the light guide remains directional but is diffused sufficiently so that an observer looking directly at the light emitting surface of the light guide will generally see uniform pleasant light.

In other embodiments, the light guide may be a rectangle, a rectangle with rounded corners, a parallelogram (possibly with rounded corners), or an ellipse. These light guides can also be formed as wedges, obviating the need for serrated grooves. Gaussian dots or other diffusers may be used.

In another rectangular luminary, the luminaries are angled with respect to the distance, and the LED strips are placed along the two house side edges only so that most of the light is directed along the distance. Prisms molded into the back surface of the light guide further control the asymmetry of the light intensity distribution. Gaussian dots or other diffusers may be used.

The LEDs may be placed inside holes formed near the perimeter of the light guide rather than LED light edge injected into the sides of the light guide.

Luminary can be used for other purposes where asymmetric light intensity distribution is required.

Other embodiments are disclosed.

1 is a perspective view of an embodiment of the present invention (luminary) used as an overhead street lamp;
2 shows the emitted light intensity (candela), showing the highest intensity directed along the street, the lower light intensity directed across the street, and the lowest light intensity directed towards the house side (opposite to the street side). ) is the light intensity distribution from the test of the lamp of FIG.
3 is a vertical plane intersecting a horizontal angle at which the emitted light intensity (candela) is maximum, showing the highest light intensity directed along the street at a slightly downward angle and the much lower light intensity directed towards the house side; The light intensity distribution from the test of the lamp of FIG. 1 .
4 is a top down view of the luminary with the top cover removed, showing the LED segments surrounding a circular light guide with a reflector sheet thereon.
5 is a bottom up view of a light guide showing Gaussian dots (about 1 mm diameter) printed on a light emitting surface. In one embodiment, the dots occupy about 1/2 of the lower surface of the light guide.
6A is a front view of a segment of series connected LEDs on a flexible printed circuit strip or rigid printed circuit board, wherein the segment includes five LEDs.
6B is a front view of another segment of series connected LEDs on a flexible printed circuit strip or rigid printed circuit board, wherein the segment contains only two LEDs for reduced light output.
7 shows an array of parallel serrated grooves formed on the back side of the light guide, opposite the surface comprising the dots.
FIG. 8 is the luminary of FIG. 7 showing LEDs emitting light into the edges of the light guide, Gaussian dots on the light emitting surface (directional but diffuse), parallel serrated grooves in the back side, and a reflector over the light guide; It is a cross-sectional view of a part of
Fig. 9 shows the luminary of Fig. 8 in which the grooves are the same and their spacing is varied.
Fig. 10 shows the luminary of Fig. 8 in which the grooves are identical and diffuse dots are printed between the grooves.
11 is a cross-sectional view of a portion of a rectangular luminary, where a wedge shape may be used in place of the grooves of FIGS. 8-10 and Gaussian dots are also used.
FIG. 12 is a top view of the luminary of FIG. 11 showing just how the LEDs need to be placed along opposite edges of the wedge-shaped light guide.
13 shows that the light guide is positioned at an angle to the distance, an array of varying-depth prisms is formed within the back surface to control an asymmetric light intensity distribution (lower intensity towards the house side) (eg, a mold); ), a top view of a flat rectangular luminary in which strips of LEDs are placed on the house side of the light guide to primarily inject light in the direction of distance only.
14 shows a single prism molded into the backside of the light guide of FIG. 13 showing how the rays from the two LED segments are reflected internally towards a distance and away from the house side. Other shapes of reflectors may be used.
Fig. 15 shows how LED segments in a circular luminary, such as that shown in Fig. 1, can output different light powers by controlling the currents in the segment to achieve a desired asymmetric light intensity distribution.
16 is a bottom view of a circular light guide having holes along its perimeter, such as 168 holes for a 15 inch luminary, to receive a ring of LEDs.
17 is a cross-sectional view of the light guide of FIG. 16 further showing the LEDs in the holes and a reflector ring over the LEDs; The light guide includes the Gaussian dots and grooves or prisms described above.
Identical or similar elements are labeled with the same number.

Although the present invention can be used in a wide variety of applications, an example optimized for use as a street lamp is shown. 1 shows a luminary 10 supported by a support structure 12 over a distance 14 . The asymmetric light intensity distribution of the luminary 10 is described for the street side and the house side. The desired light intensity distribution is high intensity light along a length of the street, lower intensity light extending across the street, and much lower light intensity emitted in the opposite direction towards the house side. Light along the length of the street mixes with light from adjacent street lights to provide fairly uniform illumination of the entire street.

The examples described below do not exhibit high luminance pixelated light patterns when viewed directly by an observer. Rather, the light is dispersed over the entire lower surface of the light emitting portion of the luminary to produce a substantially uniform diffused light that is much more pleasant than a pixelated light pattern.

Fig. 2 shows the preferred (measured in candela), obtained from the test of the lamp of Fig. 1 , in a horizontal cone with the luminary 10 at the intersection of the axes, intersecting a vertical angle at which the emitted luminous intensity (candela) is maximum. An example of the light intensity distribution 16 is shown. Many other similar distributions are achievable and the optimal distribution may depend on the particular characteristics of the distance to be illuminated. For example, for narrower distances, the distance-side intensity distribution oriented perpendicular to the distance may be concave. In the example shown, the peak light intensity directed along a distance (generally parallel to the street) is about 2-3 times higher than the peak light intensity directed perpendicular to the street, and the peak light intensity directed towards the house side is less than 1/3 of the light intensity directed directly perpendicular to the distance. This house side light can be used to illuminate narrow streets along a street or for a curb area if the luminaries are well hung into the street.

3 shows the preferred (measured in candela), obtained from testing the lamp of FIG. 1 , in a vertical plane intersecting a horizontal angle at which the emitted luminous intensity (candela) is maximum, at which the luminary 10 is at the intersection of the axes An example of the light intensity distribution 18 is shown. In the example shown, the highest peak light intensity is directed along the street at a slightly downward angle and much lower peak light intensity is directed towards the house side. The street side peak light intensity is greater than three times the peak intensity directed towards the house side.

The light intensities are substantially mirror images of the center line perpendicular to the distance.

Many other asymmetric light intensity distributions can be achieved using the structures described below.

4 is a top view of a portion of the luminary 10 of FIG. 1 with the top cover removed. A circular metal frame 20 with a lower opening was mounted around its inner perimeter with flexible circuit tape comprising a linear array of white light LEDs. White light LEDs can be high power, GaN-based, blue emitting LEDs with a YAG phosphor (which generates yellow light) to produce white light. Other phosphors may be added to achieve a desired color temperature or color rendition index (CRI).

In one embodiment, frame 20 is about 15 inches in diameter and has about 168 LEDs. The LEDs are divided into segments 22 , such as 12 segments, where the LEDs in a single segment 22 are connected in series and the segments 22 are connected in parallel. If the LED has a forward voltage of 3.5 volts, the operating voltage of the luminary 10 is about 42 volts.

The circular light guide 24 of FIG. 5 is placed in a frame 10 with printed dots 26 pointing down into the distance. The light guide 24 may be a transparent polymer, such as PMMA, about 4-5 mm thick. The printed dots 26 will be more fully described later with respect to FIG. 8 .

A reflector sheet 28 (FIG. 4) is placed over the light guide 24 and the LEDs to reflect all the light down (reflector sheet 28 is shown smaller so as not to obscure the LEDs). In one embodiment, the reflector sheet 28 may be a reflective or slightly diffusive mirror sheet to substantially retain the directivity of the rays to better control the asymmetry of the light intensity distribution. In another embodiment, the reflector sheet 28 may have a white surface to greatly increase the diffusion of light. The reflector sheet 28 may be separate from the light guide 24 or may be directly above the light guide surface.

A metal cover (not shown) is attached over the luminary 10 .

In one embodiment, to provide more control over the asymmetry of the light intensity distribution, the LED segments 22 are designed to emit different amounts of light. FIG. 6A shows the high brightness to emit along the rear portion (house side) of the luminary 10, such as in the positions shown in FIG. 4, such that the high brightness is directed along the street and away from the house side. A designed LED segment 30 is shown. Five LEDs 32 are shown connected in series by a conductor 34 on a flex circuit 36 . In a practical embodiment, there may be about 14 LEDs in segment 22 . LEDs 32 generally have Lambertian emission.

6b shows another LED segment 38 that may also be used in the luminary 10 to output reduced brightness. In this example, only two LEDs 32 are in segment 38 . Segments 38 may be placed in the positions shown in FIG. 4 to provide low brightness in the direction of the house side.

The LED segments 22 in different positions around the light guide 24 may be designed with different light outputs to further customize the light intensity distribution. Alternatively, different currents may be applied to the same LED segments 22 to customize the light output from the segments 22 .

In one embodiment, each segment 22 around the light guide is the same and receives the same current, and the light intensity distribution of the lamp can be customized using other techniques, such as those described below.

FIG. 7 shows the light guide 24 of FIG. 5 showing parallel grooves 40 molded or machined into the surface of the light guide 24 opposite the surface with dots 26 . The grooves 40 are serrated. The width of each groove 40 may be 0.5-4 mm. The grooves 40 redirect the impinging light down towards the street side and reduce the amount of light internally reflected back from the edges of the light guide 24 .

8 is a cross-sectional view of the luminary 10 showing one embodiment of the grooves 40 and printed dots 26 . LEDs 32 mounted on flex circuit 36 are shown emitting white light into light guide 24 . Light generally reflects from the smooth interior surfaces of the light guide 24 by TIR until the light is reflected down by the angled groove 24 or impinges on the translucent dot 26 . The dots 26 are epoxy-based and diffuse particles (e.g., TiO) that only slightly diffuse the light by scattering the light with a HWHM of about 12 degrees focused around the direction of the impinging ray 42, for example. ₂ , high index micro-beads, etc.). This retains some directivity of the impinging light, but diffuses the light sufficiently so that the luminaries appear uniformly white to the viewer. Some of the diffused light from dot 26 is also reflected back into light guide 24 and ultimately escapes.

The grooves 40 have a length parallel to the distance, and the beveled surfaces of the grooves 40 are angled down to receive most of the incident light from the house side LEDs (on the left). Note how the grooves 40 get deeper and deeper into the light guide 24 at increasing angles to gradually increase the chances that the ray coming from the house side of the luminary is reflected down by the groove 40 . This greatly reduces the amount of light that will be reflected back from the right edge of the light guide 24 towards the house side to reduce the amount of light emitted towards the house side. Also, the varying depths/angles of the grooves 40 allow light from the house-side LEDs to be more uniformly directed towards the light exit face of the light guide 24 , because the house-side LED in the light guide 24 . This is because the amount of light from the beams gradually decreases as they are emitted along the length of the light guide 24 while increasingly being blocked by the varying depth/angle grooves 40 . Thus, while still maintaining the asymmetric light intensity distribution shown in FIGS. 2 and 3 , there is good uniformity of light on the light exit surface of the light guide 24 .

Conversely, the generally vertical surfaces of the angled grooves 40 allow more of the street side LED light to be reflected back towards the street side to increase light emission from the street side. Since the street side LEDs are placed around the front 180 degrees of the light guide 24 , the light from the street side LEDs will be reflected away from the house side and emitted towards the street. In another embodiment, the grooves 40 will all have the same angle and become deeper and deeper, and the widths of the grooves 40 gradually increase towards the distance side.

Any light exiting from the top of the light guide 24 is reflected back into the light guide 24 by the reflector sheet 28 . As noted above, the reflector sheet 28 may be reflective (for maximum directivity), diffusely reflective, or white (for minimum directivity).

In one embodiment, about 50% of the light entering the light guide 24 exits undiffused by the dot 26 , and the remaining 50% is diffused by the dot 26 , because the dots 26 exit the light guide. Because it covers about half of the lower surface of (24). The dots 26 may be other than hemispherical, such as a rounded rectangle, a rounded triangle, flat top circles, flat side prisms, or other suitable shapes that produce diffused Gaussian emission.

By controlling the depths of the grooves 40 and their angles, the light intensity distributions of FIGS. 2 and 3 can be obtained. Additional control over the distributions can be obtained by controlling the relative light output power of the various LED segments 22 ( FIG. 4 ).

Fig. 9 shows the luminary of Fig. 8 in which the grooves 43 in the light guide 44 are identical and their spacing is varied. The grooves 43 come closer together as the grooves 43 approach the street side to reflect more light down. Because the light from the house-side LEDs is gradually reduced along the light guide 44 , the increased density of the grooves 43 is more uniform when the light along the light exit surface of the light guide 44 is viewed directly. make it

In another embodiment, the grooves 43 are evenly spaced while still achieving the asymmetric light intensity distribution of FIGS. 2 and 3 , because light from the house-side LEDs is generally directed to the angled surfaces of the grooves 43 . This is because light from the street side LEDs is generally reflected back (and ultimately downward) by the vertical surfaces of the grooves 43 facing the street side LEDs.

FIG. 10 shows the luminary of FIG. 8 , but here the grooves 45 in the light guide 46 are the same, and diffuse Gaussian dots 26 are printed between the grooves 45 . The dots 26 redirect the incident rays up and down in a diffuse/directional manner. The upwardly redirected light is reflected downwards by the reflector sheet 28 . The light exit face of the light guide 46 may have a diffusion layer 47 , such as with laminated sheets, or may be formed by machining or molding the light guide 46 . The amount of diffusion must be limited to achieve the asymmetric light intensity distribution of FIGS. 2 and 3 .

Other diffusing elements may be formed on the grooved surface, such as roughening the surface or molding prisms into the surface.

Although circular luminaries have some advantages over rectangular luminaries, good asymmetric light intensity distributions can still be achieved using rectangular luminaries. 11 is a cross-sectional view of a rectangular light guide 50 having an angled top surface (wedge shape) covered with a reflective sheet 52 . 12 is a top view of the luminary of FIG. 11 . The angled top surface allows most of the light emitted by the house side LEDs (left) to exit the light guide 50 away from the house side. The light may either exit directly from the light guide 50 or be slightly diffused by the dots 26 . Much of the light emitted by the street side LEDs is reflected from the opposing flat wall of the light guide 50 and redirected out by the angled top surface and dots 26 .

13 is a top view of a flat (non-wedge) light guide 56 angled to distance, such that its front sides are at a 45 degree angle to distance. Strips of LEDs 58 and 60 are disposed along adjacent sides of light guide 56 on the house side. Light from the LEDs is directed in the direction of the distance. To redirect light down and sideways within a distance, an array of prisms 62 shown in FIG. 14 is molded into the backside of light guide 56 to redirect rays 63 towards a distance. The position of the strips of LEDs 58/60 primarily controls directivity towards the street and away from the house side. Some light is reflected back from opposite edges of the light guide 56 and produces a small house side emission. The angles of the prism walls can be controlled to produce the asymmetric light intensity distribution of FIGS. 2 and 3 , or other desired distributions. Gaussian dots may be printed on the light emitting surface of the light guide 56 .

FIG. 15 shows the general luminary of FIG. 4 in which the LED segments 64 have their brightness controlled by selecting different currents for the segments 64 using the current control circuit 66 . Circuit 66 can be a passive circuit (eg, resistors or metal interconnect pattern) or a device that can be electronically controlled to achieve the desired light intensity distribution of the luminary.

Instead of mounting the LEDs around the edge of the light guide, separated by an air gap or more directly optically coupled, LEDs on a flex circuit are mounted around the perimeter of the light guide, as shown in FIGS. 16 and 17 . It may be disposed inside the formed holes. 16 shows through holes 70 formed around the perimeter of the light guide 72 . In one embodiment, LEDs 74 ( FIG. 17 ) may be arranged in segments similar to those shown in FIG. 4 . A flex circuit 76 supporting the LEDs 74 is formed in the ring. A reflective ring 78 is disposed over the top of the holes 70 and may also cover the light guide 72 . The light guide 72 may include the previously described grooves ( FIGS. 8-10 ) and Gaussian dots 26 to create the asymmetric light intensity distribution of FIGS. 2 and 3 .

The LEDs 74 in the holes 70 of FIG. 17 may be side emitting, wherein a reflective layer is formed directly over the top surface of the LED dies over the phosphor.

Elliptical luminaries are also envisioned.

Many different luminary designs are contemplated using the techniques described herein to generate light having a distribution in which much more light is emitted around another arc than another arc. For example, if luminaries are used to illuminate a narrow sidewalk and are placed only about 1 foot from the ground, they can be relatively small (eg, 4 inches in diameter), and they have very wide and narrow side lobes, narrow sidewalks. It can have a much shorter front lobe for , and a light intensity distribution with essentially no house side emission. Similar luminaries can be used to illuminate a room to more evenly highlight the walls, where the light is more evenly distributed along the walls.

While particular embodiments of the present invention have been shown and described, changes and modifications may be made to those skilled in the art in its broader aspects without departing from the invention, and therefore, the appended claims provide that It will be apparent that the intent is to embrace all such changes and modifications that come within the true spirit and scope of the invention.

Claims (15)

A lighting system comprising:
a light guide, wherein the light guide is configured to receive light from a plurality of light emitting diodes disposed proximate to a perimeter of the light guide;
the perimeter comprises a first perimeter location;
The received light can be guided inside the light guide as guided light,
the light guide has a light emitting surface, the light emitting surface configured to cause at least a portion of the guided light to exit the light guide through the light emitting surface;
the light guide has a reflective surface opposite the light emitting surface;
the reflective surface is configured to reflect at least a portion of the guided light such that the reflected portion remains within the light guide as guided light;
the reflective surface comprises a plurality of grooves extending parallel to each other along the reflective surface;
each groove extends into the reflective surface;
each groove comprising a first surface inclined towards said first circumferential position at a respective inclined surface inclination angle;
each groove comprising a second surface adjacent to the first surface oriented orthogonal to the light emitting surface;
The grooves increase in depth as the distance from the first circumferential position increases,
the inclined surface inclination angle changes such that an acute angle between the first surface and the second surface decreases with increasing distance from the first circumferential location;
and the second surfaces are configured to reflect light away from the first circumferential location such that a majority of the light emitted from the light emitting surface is in a direction away from the first circumferential location. According to claim 1,
the light emitting surface comprises a plurality of Gaussian diffusion dots printed on the light emitting surface;
wherein each Gaussian diffusing dot comprises a plurality of microbeads disposed in an epoxy-based material, the microbeads having an index of refraction different from the index of refraction of the epoxy-based material. The reflective surface of claim 1 , further comprising a reflector positioned adjacent and parallel to the reflective surface, the reflector configured to reflect guided light exiting the light guide through the reflective surface back towards the reflective surface. Being a lighting system. The lighting system of claim 1 , further comprising the plurality of light emitting diodes disposed proximate the perimeter of the light guide and configured to direct light into the light guide to form the guided light. 5. The method of claim 4,
the plurality of light emitting diodes are divided between individual segments around the perimeter of the light guide;
wherein a first individual segment of the individual segments and a second individual segment of the individual segments comprise different numbers of light emitting diodes. 5. The method of claim 4,
the plurality of light emitting diodes are divided between individual segments around the perimeter of the light guide;
the light emitting diodes in each of the individual segments are electrically connected in series;
wherein the individual segments are electrically connected in parallel. 5. The method of claim 4,
the plurality of light emitting diodes are divided between individual segments around the perimeter of the light guide;
The lighting system further comprises a controller configured to supply power to the individual segments, the controller supplying a first current to a first individual one of the individual segments and to a second individual one of the individual segments and supply a second current different from the first current. 8. The method of claim 7,
the first individual segment of the individual segments and the second individual segment of the individual segments comprise the same number of light emitting diodes;
the first current operatively establishes a first luminance for the first segment;
and the second current operatively establishes, for the second segment, a second luminance different from the first luminance. A method for emitting light, comprising:
using the light guide to receive light from a plurality of light emitting diodes positioned proximate a perimeter of the light guide, the perimeter comprising a first perimeter location;
directing the received light as guided light into the light guide;
directing at least a portion of the guided light through a light emitting surface of the light guide to exit the light guide;
reflecting at least a portion of the guided light using a reflective surface of the light guide, the reflective surface positioned opposite the light emitting surface, the reflected portion remaining as guided light within the light guide ,
the reflective surface comprises a plurality of grooves extending parallel to each other along the reflective surface;
each groove extends into the reflective surface;
each groove comprising a first surface inclined towards said first circumferential position at a respective inclined surface inclination angle;
each groove comprising a second surface adjacent to the first surface oriented orthogonal to the light emitting surface;
The grooves increase in depth as the distance from the first circumferential position increases,
the inclined surface inclination angle changes such that an acute angle between the first surface and the second surface decreases with increasing distance from the first circumferential location;
and the second surfaces are configured to reflect light away from the first circumferential location such that a majority of the light emitted from the light emitting surface is in a direction away from the first circumferential location. A lighting system comprising:
a light guide having a circular perimeter;
a plurality of light emitting diodes positioned proximate a perimeter of the light guide and configured to direct light as guided light into the light guide toward a center of the light guide, the perimeter comprising a first circumferential location do,
the light guide has a light emitting surface, the light emitting surface configured to cause at least a portion of the guided light to exit the light guide through the light emitting surface;
the light guide has a reflective surface opposite the light emitting surface;
the reflective surface is configured to reflect at least a portion of the guided light such that the reflected portion remains within the light guide as guided light;
the reflective surface comprises a plurality of grooves extending parallel to each other along the reflective surface;
each groove extends into the reflective surface;
each groove comprising a first surface inclined towards said first circumferential position at a respective inclined surface inclination angle;
each groove comprising a second surface adjacent to the first surface oriented orthogonal to the light emitting surface;
the plurality of light emitting diodes are divided between individual segments around the perimeter of the light guide;
a first respective one of the individual segments is configured to produce light having a first luminance, and a second individual one of the individual segments is configured to generate light having a second luminance different from the first luminance;
The grooves increase in depth as the distance from the first circumferential position increases,
the inclined surface inclination angle changes such that an acute angle between the first surface and the second surface decreases with increasing distance from the first circumferential location;
and the second surfaces are configured to reflect light away from the first circumferential location such that a majority of the light emitted from the light emitting surface is in a direction away from the first circumferential location. The lighting system of claim 10 , wherein the first individual one of the individual segments and the second individual one of the individual segments comprise different numbers of light emitting diodes. The lighting system of claim 10 , further comprising a controller configured to power the individual segments. 13. The method of claim 12,
wherein the controller is further configured to supply a first current to a first individual of the individual segments and supply a second current to a second individual of the individual segments, a second current different from the first current;
the first individual segment of the individual segments and the second individual segment of the individual segments comprise the same number of light emitting diodes;
the first current operatively establishes the first luminance for the first segment;
and the second current operatively establishes the second luminance for the second segment. delete delete

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